Setting a stop Breakpoint at a
Line of Source Code

You can set a breakpoint at a line number, using the stop at command,
where n is a source code line number and filename is an optional program file name qualifier.

(dbx) stop atfilename:n

For example

(dbx) stop at main.cc:3
:

If the line specified is not an executable line of source code, dbx sets the breakpoint at the next executable line. If there is no
executable line, dbx issues an error.

You can determine the line at which you wish to stop by using the file command to set the current file and the list command
to list the function in which you wish to stop. Then use the stop
at command to set the breakpoint on the source line: